Prevalence and key perinatal risk factors of autism spectrum disorder among toddlers in Ca Mau province, Vietnam

Introduction

Autism spectrum disorder (ASD) is a complex neurodevelopmental disorder characterized by a range of symptoms and severity levels. The term “spectrum” reflects the diversity in the presentation of the disorder, which is typically marked by challenges in communication, social interaction, and the presence of restricted, repetitive behaviors and activities (1). According to the Centers for Disease Control and Prevention (CDC), the current prevalence rate of ASD is estimated at 3.2% in the United States (2) and a discernible upward trend observed in recent years (3-5). In contrast, studies in Vietnam report a prevalence of 0.752%, based on large-scale population studies that are intended to represent the Vietnamese population (6,7). However, these studies often utilize diagnostic criteria from Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-5) for children under the age of 36 months, which may limit their applicability given the updated criteria in DSM-5 (7).

The consequences of ASD are profound, leading to significant psychological, social, and economic impairments. As a result, ASD represents a substantial burden for both families and society at large. Numerous studies have identified various factors associated with the development of ASD (8-11), including individual and familial variables such as sex, birth order, parental age, socio-economic conditions, family history, genetic predispositions, as well as prenatal, perinatal, and postnatal factors. Environmental influences have also been recognized as contributing to the onset of the disorder.

In Vietnam, diagnostic and intervention services for children with ASD are provided by healthcare units, educational institutions, rehabilitation centers, and psychological counseling services (7,12). However, these services are primarily concentrated in major cities, with rural areas, particularly in mountainous and remote regions, lacking specialized healthcare facilities for ASD diagnosis and treatment. Notably, Ca Mau is located at the southernmost tip of Vietnam and is predominantly composed of rural and remote areas. The province faces considerable challenges due to limited healthcare resources and underdeveloped transportation infrastructure. As a result, access to specialized healthcare services for the diagnosis and intervention of ASD remains significantly restricted. The identification of ASD prevalence is critical not only for raising awareness but also for informing public policies aimed at addressing the disorder, particularly in high-risk groups.

Recent studies have suggested a noticeable increase in the prevalence of ASD (9), raising questions about whether this is a true rise in incidence or simply the result of improved diagnostic criteria and greater awareness. In the clinical context, the use of standardized screening tools, such as the Modified Checklist for Autism in Toddlers, Revised with Follow-Up (M-CHAT-R/F), is essential for the early detection and intervention of ASD (13). Studies have shown that the M-CHAT-R/F is an effective tool for identifying children at risk for ASD in diverse populations (6,14). Besides that, the American Academy of Pediatrics’ 2020 guidelines emphasize early identification and individualized management, underscoring the importance of a comprehensive, multidisciplinary approach in managing ASD (15).

This research seeks to provide essential data that will inform early intervention strategies and shape policy decisions, ultimately improving the diagnosis and management of ASD in Vietnam. The study has two key objectives: the primary objective is to determine the current prevalence of ASD among Vietnamese children aged 18 to 36 months, using the DSM-5 criteria and the M-CHAT R/F screening tool, while the secondary objective is to examine the factors associated with the development of ASD in this age group. We present this article in accordance with the STROBE reporting checklist (available at https://pm.amegroups.com/article/view/10.21037/pm-25-63/rc).

Methods

Study participants

This research utilized a descriptive cross-sectional study design aimed at determining the prevalence of children at risk for ASD and identifying potential associated factors among children aged 18 to 36 months who were attending preschool and kindergarten institutions within Ca Mau province, Vietnam, from January 2022 to September 2022. The inclusion criteria for this study required that children be enrolled in preschools or kindergartens located in Ca Mau, with parental or caregiver consent obtained for participation. The caregivers, including parents and teachers, were required to agree to the child’s involvement in the study. Exclusion criteria included cases where the participants or their caregivers provided incomplete responses to the study questionnaires, which would preclude meaningful analysis of the data.

The research was carried out across 117 institutions, covering a comprehensive sample of children within the province. A total of 3,639 children participated in the study, with all eligible children from the selected institutions being included. A complete enumeration sampling method was employed, meaning that all children who met the inclusion criteria were automatically enrolled in the study, providing a broad and representative sample of the population.

Data collection and measures

The primary objective of this study was to assess the risk of ASD in children aged 18 to 36 months and to explore the factors associated with the disorder. Data collection involved the administration of a structured questionnaire to parents, caregivers, and teachers through face-to-face interviews. The questionnaire gathered essential demographic information, along with specific details relevant to the study’s aims. The severity of ASD is classified into three levels according to the DSM-5 criteria. Specifically, ‘mild’ refers to individuals requiring support; ‘moderate’ refers to those requiring substantial support; and ‘severe’ refers to those requiring very substantial support.

To assess the likelihood of ASD, M-CHAT-R/F, a validated screening tool, was used. This tool was employed to identify children who may be at risk for ASD, based on behavioral signs and developmental milestones. The M-CHAT-R/F is widely recognized for its reliability in early detection and is considered an effective instrument for screening children in this age group.

This study aimed not only to determine the prevalence of ASD risk but also to explore the various factors contributing to the disorder, including demographic characteristics and environmental influences. By using a comprehensive and systematic approach to data collection, the study sought to provide valuable insights into the prevalence and risk factors for ASD in a large sample of children in Vietnam.

Data collection procedure

The data collection process was conducted through a structured, multi-step protocol. Initially, Can Tho University of Medicine and Pharmacy developed a research plan and submitted it to the Department of Education and Training, the Department of Health, and the Department of Science and Technology of Ca Mau Province for approval. Following this, the Department of Education and Training issued official communications to the Education and Training Offices of all nine cities and districts within the province.

Each preschool in these areas was then asked to compile a list of children aged 18 to 36 months. Subsequently, nine training sessions were organized—one in each city/district—aimed at instructing selected school personnel on how to use the M-CHAT-R screening tool. Each preschool delegated two participants to the training, typically including one member of the school’s administrative board and one active classroom teacher. The training covered guidelines for administering and interpreting the M-CHAT-R, identifying related factors, and included hands-on practice with the tool.

Following the training, teachers administered the M-CHAT-R questionnaires to eligible children, in coordination with the children’s parents or guardians. Children who screened positive were then re-evaluated by study physicians using the Follow-Up section of the M-CHAT-R/F (Appendix 1). A list of children with positive M-CHAT-R/F results was compiled and referred to pediatricians and child psychiatrists. Final diagnoses were established based on the DSM-5 diagnostic criteria to confirm the presence or absence of ASD.

Data analysis

Data for this study were collected and analyzed using SPSS 26.0 software. Descriptive statistics were performed for the first objective, with categorical variables presented as frequencies and percentages, and continuous variables summarized by mean and standard deviation. For the subsequent objective, inferential statistics were employed to analyze the associated factors of ASD. The relationship between these factors was tested for significance using univariate logistic regression models, with variables considered statistically significant if the P value was less than 0.05. For those variables that were found to be significant, multivariate analysis was then conducted to further explore the true correlation between them.

Ethics approval

This study was conducted in full compliance with established ethical standards. Detailed information regarding the study’s aims and procedures was clearly communicated to all legal representatives. Participation was strictly voluntary, with guardians offering their full cooperation throughout the research process. Importantly, participants were assured of their right to decline or withdraw from the study at any point without compromising the quality of care afforded to their children. This study was conducted in accordance with the Declaration of Helsinki and its subsequent amendments. The study was approved by institutional ethics committee of Can Tho University of Medicine and Pharmacy (No. 261/PCT-HĐĐĐ, dated 28/8/2020) and informed consent was taken from all individual participants’ legal guardians.

Results

From January to September 2022, the study was participated from a total of 3,639 children aged 18 to 36 months attending preschool and kindergarten institutions in Ca Mau province. The demographic characteristics of the study participants are summarized in Table 1. The large number of children was in the 24- to 36-month age group, comprising 94.3% of the sample, while 5.7% were aged 18 to 24 months. The gender distribution was nearly equal, with 49.5% of the participants being male and 50.5% female.

Prevalence and severity of ASD

The screening and diagnostic process for ASD risk in the cohort of 3,639 children revealed that 3,404 children (93.6%) scored between 0 and 2 on the M-CHAT-R, indicating no significant risk for ASD. The remaining 235 children were further assessed using the M-CHAT-R/F tool. Out of these, 203 children were identified as being at risk for ASD, and 75 children received a confirmed diagnosis of ASD according to the DSM-5 criteria. Of those diagnosed, 17 children (22.7%) were classified as having severe ASD, while 58 children (77.3%) were diagnosed with moderate to mild ASD. The diagnostic process effectively categorized the children into risk levels, contributing to the identification of prevalence rates, classification for intervention, and the development of an early detection model for ASD within the community (Figure 1).

Figure 1 The screening and diagnostic process for ASD. ASD, autism spectrum disorder; CI, confidence interval; DSM-5, Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition; M-CHAT-R/F, Modified Checklist for Autism in Toddlers, Revised with Follow-up; M-CHAT-R, Modified Checklist for Autism in Toddlers, Revised; OR, odd ratio.

The overall prevalence of ASD in Ca Mau province was found to be 2.0%, or approximately 20 children per 1,000. This finding is consistent across various districts within the province. Table 2 and Figure 2 showed the ASD prevalence rates across different districts. The highest prevalence rates were observed in the districts of Dam Doi (2.7%) and Cai Nuoc (2.6%), while the lowest prevalence was recorded in Phu Tan district, where the rate was 1.3%. Additionally, the data indicated that children residing in districts closer to the city had higher rates of ASD compared to those in more rural areas (Table 2). Among the 75 children diagnosed with ASD, the distribution of severity was as follows: 27/75 had mild ASD, 31/75 had moderate ASD, and 17/75 had severe ASD.

Figure 2 Administrative boundary map of Ca Mau Province, Vietnam (2020–2024).

Associated factors for ASD

Several perinatal factors were found to be significantly associated with an increased risk of ASD. As shown in Table 3, children born via medical intervention (e.g., caesarean section or assisted birth) had a higher risk of ASD, with 4.2% of these children being diagnosed with ASD, compared to 1.3% in children born without medical intervention [P<0.001, odds ratio (OR) =3.259, 95% confidence interval (CI): 2.058–5.158]. Abnormal labor duration (>24 hours) was another significant factor, with 8.3% of children in this group diagnosed with ASD, compared to only 1.8% in those without abnormal labor (P<0.001, OR =4.952, 95% CI: 2.608–9.405). Premature birth (<37 weeks) was also associated with an increased risk, as 5.9% of premature infants had ASD, compared to 1.9% in full-term infants (P=0.001, OR =3.289, 95% CI: 1.704–6.346). Neonatal asphyxia was another critical factor, with 17.9% of children diagnosed with ASD having experienced asphyxia during birth, compared to only 1.9% of those without asphyxia (P<0.001, OR =10.997, 95% CI: 4.06–29.76).

Multivariable logistic regression analysis

Multivariable logistic regression analysis further confirmed the association between medical intervention at birth, abnormal labor duration, and neonatal asphyxia with an increased risk of ASD. The regression model revealed that children born via medical intervention were 2.4 times more likely to develop ASD compared to those born without medical intervention (OR =2.442, 95% CI: 1.467–4.062, P<0.001). Children with abnormal labor durations were 2.6 times more likely to be diagnosed with ASD (OR =2.578, 95% CI: 1.193–5.554, P=0.02), and those who experienced neonatal asphyxia had a 7.4-fold higher risk of ASD (OR =7.172, 95% CI: 2.303–22.331, P<0.001). These findings highlight the importance of early medical intervention and monitoring during labor and delivery to reduce the risk of ASD (Table 4).

Discussion

Key findings

This study provides compelling evidence on the prevalence and associated factors ASD in children aged 18–36 months in Ca Mau province, Vietnam. The overall prevalence of ASD was found to be 2.0%, which equates to approximately 20 children per 1,000. Additionally, the study identified key perinatal risk factors associated with increased ASD risk, including medical interventions during delivery, prolonged labor, neonatal asphyxia, and preterm birth. These findings underscore the importance of early recognition and tailored intervention strategies for at-risk children.

Strengths and limitations

This study has several strengths, including its large sample size of 3,639 children, which provides robust data for estimating ASD prevalence in a rural province of Vietnam. The use of the M-CHAT-R/F screening tool, coupled with DSM-5 diagnostic criteria, enhances the reliability and validity of the findings. Furthermore, the study’s inclusion of multiple districts across Ca Mau allows for a comprehensive assessment of the geographic variation in ASD prevalence. However, there are limitations to consider. The cross-sectional design of the study limits the ability to draw causal inferences, and the reliance on parental and caregiver reports for data collection introduces potential bias. Additionally, the study was limited to a single province, and thus, its findings may not be fully generalizable to other regions of Vietnam, particularly urban areas where diagnostic practices may differ.

Comparison with similar research and explanations of findings

The prevalence of ASD in our study (2.0%) is comparable to that reported in several other international studies (1,16), and reflects a rising trend in ASD diagnoses globally. This rate is also higher than earlier Vietnamese studies, such as that by Le Thi Vui and Hoang Van Minh (7,17,18), which reported a prevalence of 0.76% using DSM-IV criteria, suggesting that updated diagnostic frameworks (e.g., DSM-5) and validated tools (M-CHAT-R/F) may improve detection sensitivity. Moreover, a meta-analysis showed that 0.77% of children globally are diagnosed with ASD (19). Compared to a study conducted in northern Vietnam, the prevalence observed in our study was more than twice as high (7). This discrepancy may, in part, be attributed to the socioeconomic context of our study area, where there is still limited public awareness regarding psychological and developmental issues in children. Many caregivers may not recognize the signs of ASD, leading to a general lack of concern or attention to this condition. Therefore, the findings of our study underscore the need for greater attention from the healthcare system to address ASD-related issues in underserved regions such as this one.

In comparison with regional studies, a population-based study in Thailand using M-CHAT-R/F and DSM-5 reported a prevalence of 1.6% in urban settings, slightly lower than ours, which may be attributed to geographic differences, healthcare access, or public awareness (14,20). Moreover, a multicenter study across Southeast Asia by Hossain et al. identified underdiagnosis in rural areas due to lack of trained personnel and diagnostic resources (9), emphasizing the value of community-based screening as applied in our study.

Regarding perinatal risk factors, our findings corroborate recent global evidence linking obstetric complications with ASD. For instance, a large-scale meta-analysis by Chen et al. (8) confirmed that cesarean delivery is associated with a 1.33-fold increased risk of ASD, likely due to shared genetic or environmental factors. Similarly, a study by Yuan et al. identified prolonged labor as a significant risk factor, potentially linked to fetal distress or hypoxia, which aligns with our finding of an OR of 2.37 for verbal or behavioral responsiveness (10).

Birth asphyxia was the strongest associated factor in our study (OR =7.172), which is in line with recent cohort studies in China, where neonatal hypoxia was consistently linked to elevated ASD risk, possibly due to impaired neurodevelopment from early hypoxic-ischemic injury (10). In terms of diagnostic tools, our study reaffirms the high diagnostic accuracy of M-CHAT-R/F, with sensitivity (98.67%) and specificity (95.48%) consistent with global evaluations (13). Recent studies reported comparable metrics in both clinical and community settings, supporting its utility in early ASD screening even in low-resource environments (11,21).

Together, these findings indicate that ASD prevalence in rural Vietnam is approaching that of more developed regions, particularly when robust tools and criteria are used. They also reinforce the importance of perinatal monitoring and timely screening, which are critical in mitigating long-term developmental consequences.

Implications and actions needed

The rising prevalence of ASD, as evidenced by this study, has significant implications for public health and healthcare infrastructure. The findings highlight the critical need for increased resources dedicated to early screening and diagnostic services, especially in rural and underserved areas. The identification of perinatal factors associated with ASD also calls for targeted interventions and prevention strategies aimed at reducing the risk of these complications during pregnancy and childbirth. For example, implementing training programs for midwives in remote and underserved areas may help lower the risk of perinatal complications in children. Furthermore, the study underscores the importance of integrating ASD screening into routine pediatric care, particularly in regions with limited access to specialized services. It also suggests that enhancing public awareness of early signs of ASD could facilitate earlier detection and more effective intervention, ultimately improving long-term outcomes for children with ASD.

While this study provides valuable insights into the prevalence and risk factors for ASD in Vietnam, further research is needed to explore the underlying mechanisms and longitudinal outcomes of the identified risk factors. Specifically, future studies should examine the role of genetic predispositions, environmental factors, and the interplay between prenatal and postnatal influences on the development of ASD. Additionally, there is a need for prospective cohort studies to better understand the long-term impacts of early interventions on children diagnosed with ASD. Further work could also explore the effectiveness of various intervention models in different socio-economic and geographic contexts within Vietnam to inform tailored, community-based programs.

Conclusions

In conclusion, this study provides an important contribution to the growing body of knowledge on the prevalence and risk factors of ASD in Vietnam. The findings demonstrate a higher prevalence of ASD than previously reported, particularly among children with perinatal risk factors. These results highlight the need for improved early detection and intervention strategies to address ASD in both urban and rural settings. By enhancing awareness, access to diagnostic services, and early intervention programs, we can mitigate the long-term impact of ASD on affected children and their families. Further research into the underlying causes and effective treatments for ASD will be crucial in advancing our understanding of this complex neurodevelopmental disorder.

Acknowledgments

To complete this study, we would like to express our sincere gratitude to Can Tho University of Medicine and Pharmacy and Can Tho Pediatric Hospital for their invaluable support. We also extend our heartfelt thanks to the pediatric patients and their families who participated in this research.

Footnote

Reporting Checklist: The authors have completed the STROBE reporting checklist. Available at https://pm.amegroups.com/article/view/10.21037/pm-25-63/rc

Data Sharing Statement: Available at https://pm.amegroups.com/article/view/10.21037/pm-25-63/dss

Peer Review File: Available at https://pm.amegroups.com/article/view/10.21037/pm-25-63/prf

Funding: None.

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://pm.amegroups.com/article/view/10.21037/pm-25-63/coif). The authors have no conflicts of interest to declare.

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. This study was conducted in accordance with the Declaration of Helsinki and its subsequent amendments. The study was approved by institutional ethics committee of Can Tho University of Medicine and Pharmacy (No. 261/PCT-HĐĐĐ, dated 28/8/2020) and informed consent was taken from individual participants’ legal guardians.

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.

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